Inactivation Mechanisms of Escherichia Coli in Drinking Water Using Reactive Species Generated from a Surface Discharge

Bacterial and chemical contaminations of drinking water imperil the health of people.A reactive species injection method is presented for sterilizing drinking water.To produce reactive species,a gas phase surface discharge reactor(SDR) is designed: a spiral stainless steel wire attached on the inside wall of a quartz glass tube is used as the high voltage electrode,and the drinking water is the ground electrode.The performance and mechanisms of the method in inactivating of Escherichia coli(E.coli) are analyzed.Experimental results show that 500 mL E.coli-contaminated drinking water(108CFU/mL) is completely sterilized within 4 min.Based on the scanning electron microscope(SEM) analysis,there were plasma-induced cell structure damages of the E.coli in the sterilized water,and the damage resulted in the leakage of protein,which was proved by chemical analyses.Meanwhile,the heating effect concomitantly generated by discharge plasma does not influence E.coli inactivation,and the contribution of direct ultraviolet(UV) irradiation could be neglected too.The ozone generated by SDR and the hydroxyl radicals(·OH) subsequently generated in drinking water play the decisive roles in E.coli inactivation because these reactive species cause the cell rupture.